Members of the fractious Washington Teachers Union, sparring over a proposed three-year contract, are conducting a ratification vote this week on the agreement that would raise salaries by 20.5 percent.

"We're trying to maintain what we've had before, and we've done that," said William H. Simons, who regained the union presidency in a bitter five-way fight last spring. "It's a good contract."

Simons noted that the tentative agreement contains no increase in the teachers' workday, which remains the shortest in the area, even though the school board had sought to lengthen it.

But Harold Fisher Jr., whom Simons ousted, said the union should have negotiated bigger raises and accused Simons of "giving up things that we held sacred for 20 years" since the first union contract in 1967. "The school board ate him up in this contract," Fisher said.

Similar criticism has been voiced by other longtime opponents of Simons, including teacher Emily Washington, who organized a demonstration outside union headquarters on Friday. But Simons said the contract has been endorsed unanimously by the union's 12-member negotiating committee and 23-member executive board.

The union's 5,000 members are voting by mail with ballots due Friday, and counting will take place on Saturday. Afterward the school board is expected to ratify the pact.

The raises in the new contract are substantially greater than the 9 percent increase in base pay over three years -- plus possible bonuses -- agreed to by other District government employees, but are smaller than the pay boosts offered in some suburban school systems.

Under the proposed agreement, teacher pay this year retroactive to Oct. 1 would range from $20,263 for beginning teachers to a $41,888 maximum for teachers with 15 years' experience and a master's degree plus 60 graduate credits. By 1990 the scale would range from $23,327 to $48,222, keeping the District pay scale in the middle among area school systems.

Because most D.C. teachers have long years of experience and advanced degrees, their average pay was $33,797 last year, the second-highest in the area after Alexandria. Under the new contract, the average would reach almost $36,000 this year.

Fisher charged that the contract would ease restrictions on involuntary teacher transfers and impose new burdens by allowing administrators to look at teachers' lesson plans at any time. He criticized Simons for agreeing to two more workdays, raising the total to 192, and for agreeing that the losers would pay the full cost of arbitrating a grievance.

"We haven't lost any rights to protect our teachers," Simons said.